Various types of electronic apparatus have hitherto been developed and become widespread. Among them, a description will be given here of a personal computer having an information computation function as an example of electronic apparatus.
In addition to a stationary personal computer in which a main unit which is equipped with a CPU, a hard disk, etc. and which performs arithmetic processing, an image display device having a display screen which displays images, a keyboard to perform key operation, etc. are constructed as separate housings, there has come into widespread use a portable personal computer, called a notebook personal computer, in which an image display section having a display screen and a main frame section which incorporates a CPU performing arithmetic processing, a hard disk to store information, etc. and on the top surface of which keys are arranged to perform the role of a keyboard are connected to each other via hinges.
In this notebook personal computer, the display section and the main frame section can be brought into a double-folded superposed condition via the hinges. Therefore, the notebook personal computer is convenient for carrying. At the same time, by opening the display section and the main frame section, it is possible to perform key operation while looking at the display screen. Thus the notebook personal computer has user-friendliness.
Because in this notebook personal computer, importance is attached to portability and emphasis is given to a low-profile design in a folded condition, its performance is considerably sacrificed in terms of functions compared to a stationary personal computer. Also, there are many cases where even a notebook personal computer is not carried and usually it is used on a desk as with a stationary personal computer. Therefore, recent years have seen the emergence of an integrated personal computer which is provided with improved functions as well as portability to a certain degree, which portability is not so high as a notebook personal computer. This integrated personal computer is typically constituted by: a base section, which is placed on a flat surface such as a desk; a standing section, which is supported by the base section and installed in a standing manner thereon and which has a display screen; and a keyboard, which is attached to the standing section via hinges and opens and closes with respect to the standing section. In the case of this integrated personal computer, when not in use, it is possible to obtain a space on the desk by putting the keyboard against the standing section in such a manner as to be superposed thereon, and the integrated personal computer is also easy to carry because of the integral type.
Many of such notebook personal computers and integrated personal computers have hinges as described above, and it is ensured that these computers are housed in a compact manner when not in use and that they are convenient for carrying (refer to Patent Documents 1 and 2, for example).
In addition to the above-described construction that enables a personal computer to be folded by providing hinges, other constructions are also conceivable. For example, the portion of the keyboard is demounted from the display section and made independent of the display section, with the result that key operation is performed, with the keyboard placed in a free position demounted from the display section, and part of the functional portions of the personal computer are removable from the main frame section (refer to Patent Document 3). In this case, however, the mechanism of mounting and demounting poses a problem, that is, by what mechanism the locking during mounting and the unlocking during demounting are performed poses a problem.
For example, the Patent Document 4 discloses a conventional general lock mechanism, although this lock mechanism is an opening and closing lock mechanism used in folding and unfolding a personal computer, and not a lock mechanism used in mounting and demounting part of the functional portions to and from the main frame section.
(Patent Document 1)
Japanese Patent Laid-Open No. 10-11189
(Patent Document 2)
Japanese Patent Laid-Open No. 11-212665
(Patent Document 3)
Japanese Patent Laid-Open No. 10-133772
(Patent Document 4)
Japanese Patent Laid-Open No. 2002-149271
FIG. 20 (A) and FIG. 20 (B) are each a diagram which shows the lock mechanism described in Patent Document 4 above in a modeled form.
A moving hook 11 is urged in the direction in which the moving hook 11 approaches a fixed locking claw 10 (the direction of the arrow A). When the moving hook 11 moves in the direction of the arrow B, a tapered surface 11a of the moving hook 11 interferes with the fixed locking claw 10 and the moving hook 11 moves or rotates toward the side opposite to the arrow A. As a result of this, the moving hook 11 further moves in the direction of the arrow B by avoiding the fixed locking claw 10, which is an obstacle, and when the interference between the moving hook 11 and the fixed locking claw 10 is lost, the moving hook 11 returns in the direction of the arrow A due to the urging force of the moving hook 11 and brought into a locked condition as shown in FIG. 20 (A).
Motions necessary for releasing this lock are shown in FIG. 20 (B). It is necessary to cause motions such that in releasing this lock, the moving hook 11 is first moved in the direction of the arrow A′ to permit movement in the direction of the arrow B′ and then moved in the direction of the arrow B′.
However, in a lock mechanism as described above, the moving hook 11 is basically moved on the same straight line (on the straight line B–B′) in a case where the moving hook 11 is locked (movement in the direction of the arrow B) and in a case where the lock is released (movement in the direction of the arrow B′). Therefore, a considerably large space is required in these directions. Also, in a case where the fixing force of the hook is to be increased, it is necessary that the engaging area of the hook be simply a large area. Also in this case, a large engaging area and a large area for the movement in the direction of the arrow A during unlocking are required, posing the problem that the lock mechanism becomes large in size.
In view of the above circumstances, the present invention which has as its object the provision of a unit mounting mechanism which can achieve miniaturization with a simple construction and can perform positive mounting and unlocking, and an electronic apparatus which is provided with this unit mounting mechanism.